Several factors distinguish the labor supply decision of older persons from that of the primary-age labor force: the availability of income maintenance in the form of old-age benefits from the Social Security program and other public support programs, income from other private and government pension plans, compulsory retirement provisions, changing preferences for leisure, deteriorating health, and scarcity of part-time jobs under semi-retirement. The standard theoretical and empirical models of the labor market must be adapted to these special features relevant to the older population. A longitudinal analysis of a simultaneous model of labor supply, market wage determination, and the asset accumulation behavior of the older population is proposed involving estimate of the factors determining labor force participation, annual hours and weeks of work, threshold labor supply quantities and reservation wages, wage offers and asset holdings The analysis will combine cross-section and over-time data using two merged micro-data files (white married males and white female heads of families), each including several hundred variables created from three panels (1969, 1971 and 1973) of the Retirement History Survey of the Social Security Administration, the largest and most detailed longitudinal survey currently available regarding the older population. The estimates of the model will be applied to analyze current patterns of behavior and trends, as well as to predict the effects of various proposed changes in social policy regarding the aged, such as modifications in the benefit structure and earnings test in the Social Security program, expanded coverage and benefits under private pension programs, the recent increase in the compulsory retirement age, and recent efforts to expand the part-time job market and to increase job mobility for older persons.